The present invention relates to film packs of the type including a plurality of film units stacked in a cartridge housing. More specifically the invention relates to such a pack, particularly of self-processing film units, having a slide plate that can be employed for a number of functions including: shielding the film units from light, supporting the film units for exposure and during processing, and transporting the film units from the pack through a camera processing mechanism.
It is well known to supply photographic film in a pack that includes a plurality of individual film units stacked in a cartridge housing. Typically, the housing has an exposure aperture covered by a dark slide which shields the units from premature exposure, called fogging. In operation, the pack is positioned in a camera, the dark slide is removed, and the film units are manipulated for sequential presentation to the exposure aperture. In accordance with the disclosure of U.S. Pat. No. 458,981, for example, a stack of transparent film units is supported by a pressure plate and spring assembly. A removable dark slide shields the units from fogging, and opaque film holders, interleaved behind each film unit, protect subsequent units in the stack from simultaneous exposure with the first unit. An exposed film unit and its holder are removed from the forwardmost position by a gear wheel, while the pressure plate and spring assembly resiliently advance the next successive unit and holder into the exposure position. Another approach is depicted in U.S. Pat. No. 424,857. In this example the film units are carried in a cartridge, and a slide, initially serving to cover the cartridge exposure aperture, is used to push the sequentially exposed film units from the forwardmost position.
The above-noted patents represent technology which was developed for use with film plates that today serve only in somewhat specialized applications. Film packs have received new attention, however, with the increase in popularity of self-processing film. In present commercial approaches, self-processing film units are not only manipulated within the pack, but are transported from the pack and camera through a mechanism that initiates processing of the film units. Typically, a pair of opposed pressure rollers rupture a chemical pouch on the film unit and distribute a processing composition from the pouch across the picture area. In U.S. Pat. Nos. 4,132,471 and 3,699,862, for example, the film units are supplied in a cartridge housing having an exposure aperture, covered by a dark slide, and an exit slot. A reciprocating camera mechanism expels the dark slide and then the film units one at a time through the exit slot, while a pressure plate and spring assembly advance the next successive film unit into the exposure position. Other approaches for transporting film in instant cameras include manual cranks, see U.S. Pat. No. 4,122,469; lanyards, see U.S. Pat. No. 3,965,480; and levers, see German Pat. No. 2,619,919.
It should be apparent from the above background that numerous approaches have been proposed for manipulating film units in a pack. Some employ a dark slide for removing the film units from the exposure position, and some advance the film units through camera processing mechanisms. It will become apparent from the following description, however, that none of these prior approaches offer the important advantages of the present invention.